French-based Electricité de France said underlying earnings fell by 2.9 per cent in the UK to é856m during 2006, after the costs of adding nearly 450,000 new UK customers to its books.

Volatile fossil fuel prices, coupled with a warm summer and mild winter, leading to reduced fuel demand, also impacted earnings at the energy giant.

The news came despite a series of price hikes in the year, which saw gas prices rise by 14.7 per cent and electricity by 4.7 per cent in March, and then again by 19 per cent and eight per cent respectively in July.